The wireless communications network has grown exponentially over the years. A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. LTE systems, also known as the 4G system, also provide seamless integration to older wireless network, such as GSM, CDMA and Universal Mobile Telecommunication System (UMTS). In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNodeBs or eNBs) communicating with a plurality of mobile stations, referred to as user equipments (UEs). The 3rd generation partner project (3GPP) network normally includes a hybrid of 2G/3G/4G systems. The Next Generation Mobile Network (NGMN) board, has decided to focus the future NGMN activities on defining the end-to-end requirements for 5G new radio (NR) systems.
When a UE is in connected state, UE location is known by the network at cell level. When a UE is in idle state, UE location is known by the network at track area (TA) level. A tracking area code (TAC) is a unique code that each operator assigns to the TA. A tracking area identifier (TAI) consists of a PLMN ID and a TAC. A UE obtains a TAI list when it attaches to an LTE/NR network. This list shows the tracking areas where the UE is located and within which the UE can travel. The LTE/NR network has to have updated location information about UEs in idle state to find out in which TA a particular UE is located. The UE notifies the LTE/NR network of its current location by sending a tracking area update (TAU) request message in EPS or a registration request message in 5GS every time UE moves between TAs.
The mobility management in 5G NR systems has two types of TAI list—a list of allowed or non-allowed TAI and a list of forbidden TAI. When a UE attaches to a network and receives an error in a registration procedure, a TAI is added into the forbidden TAI list. The forbidden TAI list is maintained in the UE, and is reset by the UE when the UE is switched off, or when a universal integrated circuit card (UICC) containing the SIM/USIM is removed, or is periodically reset. In a subsequent registration procedure, the network may provide the UE with allowed tracking areas. The allowed tracking area(s) can be removed from the forbidden TAI list if one or more tracking areas in the forbidden TAI list are received from the network. However, if the UE is registered for emergency services, then the tracking area(s) may not be removed. Furthermore, the network may provide the UE with the allowed tracking areas via a configuration update command. A proper procedure of maintaining and updating the forbidden TAI list is desired.